Machine for grinding long radius arcs



Sept. 30, 1947 c. E. HALL MACHINE FOR GRINDINQ LONG RADIUS ARCS Filed Oct. 29, 1945 5 Sheets-Sheet 1 Z/VaZZ,

Sept. 30, 1947. c. E. HALL MACHINE FOR GRINDING LONG RADIUS ARCS 'Filed 001;. 29, 1945 5 Sheets-Sheet 2 1 lNVENToR. frail/'21 Z. /fdZZ- i Hrw/vw Eys.

Sept-30,1947. QEHALL f 2,428,215

MACHINE FOR GRINDING LNG RADIUS ARCS Filed Oct. 29., 1945 3 Sheets-Sheet 5 y I. INVENTOR.

Patented Sept. 30, 1947 `2,428,215 Y MACHINEFOR GniNDING LONG o, RADIUS ARCS Calvin E.'5Hall, St. `Clair Shores, Mich., assignor to Michigan Tool Company, Detroit, Mich., a

corporation of Michigan Application october 29, 1945', salviamo. 625,334

This invention relates to grinding machines and, more particularly, relates to a grinding machine for grinding arcuate surfaces of relatively large radii.

In many instances, it is desirable in the machine tool industry to grind arcuate surfaces havingl large radii on parts which are not circular, as for example, gear crowning blocks. When such arcuate surfaces have radii beyond the capacity of present grinding machines, the problem of grinding the same is perplexing an-d difficult. 'At present, it is customary to locate a series of ordinated points on the piece to be gro-und and then s-cribe the desired arc through said points. The arc thus laid out is then ground on a grinding machine after which vit is checked by means of gage Iblocks to determine whether the correct rise has been maintained at each of the ordinated points during the grindingoperation. Inasmuch as the accuracy of the Work vdepends entirely upon the ability of the operatorythe work can only be satisfactorily completed by an excerptionally skilled operator. The time involved in a grinding operationv such as this is considerable and cost is relatively high, particularly where only one or a limited number of parts are to be produced.

" IV have discoveredV that by utilizing a simple geometric principle, itis possible to grind a considerable range of arcs of large radii, either convex or concave, with a machine, which may be either a complete grinding unit especially designed for the purpose or a fixtureadapted for use with a surface grinder. In either event, extremely accurate work may 'be accomplished by a relatively unskilled or semiskilled operator.

It is, accordingly, a primary object of this invention to provide a grinding machine for grinding a considerable range of arcuate surfaces of large radii, either convex or concave.

Another object of this invention is to provide a construction for grinding arcuate surfaces of large radii which may be either a complete grinding unit or a fixture adapted for use with a surface grinder.

A further object of this invention is to lprovide a grinding machine with which such arcuate surfaces may be ground with extreme accuracy by a relatively unskilled or semiskilled operator.

A still further object of this invention is to `provide an apparatus for grinding arcs of large radius which requires but little time to set up.

Further objects and advantages'of my invention will be apparent from the description which follows when considered in connection-with the 3 Claims.v (01,'51-96) accompanying drawings in which like numerals which certain of the parts are in phantom or broken away to more clearly show theoperation of the machine. f

Figure 2 is an Yelevation of the right the machine shown in Figure l.

Figure 3 is a front elevation of the apparatus with the Work holder omitted to more clearly show certain operating parts with the sine bars positioned for grinding a large convex arc.

Figure 4 is a front elevation similar to Figure 3 with the sine bars positioned for grinding a large concave arc. f

Figure 5 is a front elevation of a modification of the invention which may be used to grind an arcuate surface having a large radius on teeth of a machine element such as a cutter.

This grinding machine provides a pair of sine fbars which may be adjusted to slope insuch manner that they form the legs of a widely open V, the vertex of which may point toward or away from the axis of rotation of the wheel on the machine. TheseV sine bars each slidabiy mount a pivot block," which blocks are interconnected by means ofa link for mutual sliding in straightline paths intersecting at a common point. This sliding movement, eiected by means of a reciprocable rack integrally` connected to one of such pivot blocks and a rotatable pinion meshing the same, causes the link to shift'. A work holder for retaining a workpiece is mounted on this link and shifts with the same, effecting the workpiece to progressively contact the grinding wheel along a path which is an arc of a true circle, either convex or concave, depending upon the attitude of the sine bars. I

Referring to the drawings for a more detailed description, a base is provided as is generally indicated at I. On an upwardly directed post 2, a suitable bearing 3 is mounted in which shaft 4 is journaled to rotatably support a grinding wheel 5. This grinding wheel may be rotated in the usual manner by driving means located interiorly of said base. v Y

The base has a machined surface 6 to which the base plate 'I of a casting, generally indicated at 8,*is anchored by bolts 9. Such casting provides an integraLupwardly projecting back plate Ill Vwhich is properly supported by ribs. This back plate provides formounting -a pair ofsine bars I I-ancl I2 thereto by means of a plurality of bolts side of I555 I3 extending through curved. slotted openings from the front face thereof., .Immediately belnw I4 to provide for adjusting said sine bars into sloping position radially about pins I5 and i6. Such pins are secured to the sine bars by screws I1 which pass diametrically through said pins to threadably engage said sine bars. These pins 5 are then inserted into the bushings I8 and i9 providedin opeiungs--Zllfand 2 I ,extendingthroug'h back plate l0; ltiishllit obvious,r then, that the. sine bars may thus be radially moved about such pins.

At the opposite end of these sine bars, pins 22 Y and 23 are secured thereto in a similar marinier.v Pins 22 and 23, however, do not pass through back plate l0, but stop short. aslight. amount these pins, pads 24 and 25 are located. Said pads each have a ground surfaceupon which gageV blocks may be mounted to contact pins 22 and '23. In this manner, the sine bars may be placed iii-. the desired sloping adjustment after which said bars may be locked thereatby means. of the pref viously described boltsl.

. Such' sine'bars providegroovesl 26 and 21 to receive. the dovetails of pivot blocks 28 .and28 for slidable movement therein andare intercom nected for mutual movement by. plateY or link- 30. This link is pivotally mounted toA said blocks by means of pins 3|4 and 32 extending through mating openings provided in the pivot blocks and the plate 3l), respectively; The openings in the pivot blocks .are counterboredto provide'a mating sur! face4 for the shoulders onthejpinssuch as that.. indicated-at 33 in FiguretZ. The4 openings inthe plate are likewise `counterbored to receive the bushings 34 and 35andprovide amatiug surface such as that indicated at 3B, Figure2, for the. shoulders of said bushings. Such busl'ringsreceive Vpins 3l and 32. whichare held thereinby caps `3'! and 38 through` which .screws .39 pass to threadably engage a tapped opening in the respective pins. Thus, as said blocks slidably move inthe grooves providedrby the sine bars, a -pivq etal connectionis. maintainedbetween each oi said blocks and plate ).,v

This mutual slidingof- .the pivot blocksis ac. complished by means of a. reciprocable rack 4.0 and a rotatable pinion 4l. Such rackis secured tothe top of pivot bloekzbyaplurality of screws 42. In this position, the` rack meshes said pinion which is rotatably supported. upon shaft 43.. This shaft is journaled for rotationi-n bearing` 4.4 per.: pendicularto back plate.. ill and, turn, the bearing is mounted upon an. integral support anchored, to sine bar l2. 'Ihisconstruct-ion per.- rnits said bearing to shiftas the attitudef --the Sine bar varies, and, ofcourse, permits thepDQIi ilo-always positively mesh theE rack which likewise shifts with th'e sine bar-due to the-slidablecom nection between pivot block '28 and-sine v.harl2, :its .will new. becbserved that as rimandi isgotatedibymeans Qithe-.fhendwheci 45 mguntedou .the oppositeend o Ashaft 4.3, the raohwilirecim recate. effecting sdl., moyement. ci .the pvot blecks in the cranves.

.'Qensideriugenowfth p. 32. lfollow durne'tlls' Sliding mQV-Gmfls; Wil-.1 be observed that such pathsghe-jinr-straight.lines which intersect at aeentral peint.; Again. considerinethe :pi-ns aseirtrexn ies ei chord -or-a. circlewhose radius is thatoijthefarcdesired on theworkpiece. 41; it,may .be iurther-sbservedthat although the I circle. ,shifts, as ,indicatedeby .the :attitude `o f the-chord said cir. le -alw yspasses .through thissgenlfel wie@ 'resl-liilgi-lli ilede* sited are bei-ne. produced enythgfwerkrniee-f handwheel 4B may be rotated and the work- To mount workpiece 41 in position so that such arc may be ground thereon, a work holder 48 is secured to plate 30 by means of T-bolts 49 which engage T-slot 50 in said plate. This work holder provides mounting surfaces 5I and 52 disposed at right angles to each other to which the workpiece may-be secured by suitable, means, and furtherprovidesT-slot fain oneoi saidV surfaces for anchoring such' securing means. Thus, after mounting the workpiece to this work holder,

pieefied to the rotating grinding wheel to effect grinding of an arc thereon, the radius of which `issthat desired:

y scribed as: a complete grinding machine designed Yespecially forl grinding arcuate surfaces having large radii. However, this highly desirable result upmoftnigpnipt, this invention has been demal' also: be accomplished by mounting the machine as a fixture on the table of a surface grinder. In this event-casting 8^, carrying. the. various elements., may be secured. to -suchtabie and the desired. arcuate. surface generated as described in the foregoing.

Should it be. desired to manufacture arelatively large number of pieces with arcuate surfaces, vall ofwhich 'have the same large radius, it is often expedient. to grind an arc of similar radius, but. opposite prole, on the teeth of a cutter whiehmay then be used formilling the desired arcv on the, pieces. With the modified form-of my invention illustrated in Figure 5, an arcuate surface having a large, radius maybe ground on the teeth of a cutter. in this machine, a pair of braclnets` 5 4.. and 55are mounted to .plate Baby meansnf T-.bolt's 49. It isA obvious that such bracketsare adjustably mounted by means of the T=bolts inorder to accommodate cutters of various lengths.. These bracketsprovide centers 56 and 51 between which a cutter may be rotatably supported.v

In order tofacilitate-loading and unloading of the cutters; center 51 is slidabl-y maintained in position by annular compressionspring 58, which is. disposedbetween shoulder 59 on said center and one end-wall of theibracket.- In this manner, such center is held with shoulder 59 abutting shoulder 6B. provided vby bracket 51. When it is desired to-wthdrawthis center, lever 6l, which ispinned .at-,6210, such center, may be moved outwardly as indicatedby .the dash lines. vTo effect such. withdrawingyofV the center, leverg 6l. is pinnedat G3-:te a link. i4v which'. in turn, pinned. at Sfte' .anputwardly directed projection B6 of .bracket-'51. .After loading thecutter be= tween` the centers. the siidable. center may-:be securely and positively. .locked inv position by means of hand screw 81 which prevents further sliding of .the `center until. itis `againlunlocked.

When the cutter is positioned between the centers as describedf'it maybe rotated manually'or by anysuitable means as itisfed totherotating grinding. Wheel by means orhandwheeltpand the desired arc ground on the teeththereof as describedin the.. foregoir1s It will .be ,clear iromthe-.ioreseingdescription that the. vgrinchng .mach-ine shown .in the` draw,- ings and described above has been-illustrated and described in.l rather sseie detail "Obviously, many modcations.- changes, and .departures from theabove described construction may be made-Without vder aarting from the j generic spfrit and scope 'of the inve ntienA es set .forth-n ,f the appendedfclams..

What is claimed is:

1. A grinding machine for grinding arcuate surfaces of large radii, said machine having a base, a rotatable grinding wheel thereon, means to rotate said wheel, a supporting element anchored to the base, a pair of sine bars grooved throughout the length thereof and each pivotally mounted on said supporting element, said sine bars each being arcuately movable about its respective pivot to bring the sine bars into predetermined opposite sloping angular adjustment, a pivot block slidably mounted in the groove in each sine bar, said blocks each being slidably shiftable and positively guided, a plate pivotally connecting the Divot blocks, a work holder mounted on said plate and adapted to retain a workpiece for movement in the plane of rotation of the grinding wheel, a reciprocable rack mounted on one of said pivot blocks, a pinion rotatably mounted on the supporting element and adapted to engage the rack for effecting reciprocation thereof when said pinion is rotated whereby to shift said blocks and bring the workpiece .into contact with the grinding wheel along a path which is an arc of a circle.

2. A grinding machine for grinding arcuate surfaces of large radii, said machine having a base, a rotatable grinding Wheel thereon, means to rotate said wheel, a supporting element anchored to the base, a pair of sine bars grooved throughout the length thereof and each pivotally mounted on said supporting element, said sine bars each being arcuately movable about its respective pivotl to bring the sine bars into predetermined opposite sloping angular adjustment, a pivot block slidably mounted in the groove in each sine bar, said blocks each being slidably shiftable therein and positively guided, a plate pivotally connecting the blocks, a workholder slidably mounted on said plate for movement into predetermined adjusted position relative to the axis of rotation of the grinding wheel and adapted to retain a workpiece for movement in the plane of rotation of said wheel, a reciprocable rack mounted on one of said pivot blocks, a pinion rotatably mounted on the supporting element and adapted to engage the rack for eiecting reciprocation thereof when said pinion is rotated whereby to shift said blocks and bring the workpiece into contact with the grinding wheel along a path which is an arc of a circle.

3. A grinding machine for grinding surfaces of large radii, said machine having a base, a rotatable grinding wheel thereon, means to rotate said wheel, a supporting element anchored t0 the base, a pair of sine bars grooved throughout the length thereof and each pivotally mounted on said supporting element, said sine bars each being arcuately movable about its respective pivot to bring the sine bars into predetermined opposite sloping angular adjustment, a pivot block slidably mounted in the groove in each sine bar, said blocks each being slidably shiftable therein and positively guided, a plate pivotally connecting the pivot blocks, a pair of opposed brackets slidably mounted on said plate for movement into predetermined adjusted position relative to the axis of rotation of the grinding wheel, a fixed center in one bracket and a slidable center in the other bracket adapted to rotatably support a workpiece therebetween, means on the last named bracket to shift the slidable center therein for removing a workpiece without disturbing the adjusment of the brackets, means on said last named bracket to lock said slidable center therein during a grinding operation, a reciprocable rack mounted on one of said pivot blocks, a pinion rotatably mounted in the supporting element and adapted to engage said rack for effecting reciprocation thereof when said pinion is rotated whereby to shift said blocks and bring the workpiece into contact with the grinding wheel along a path which is an arc of a circle.

CALVIN E. HALL.

REFERENCES CITED IThe following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 2,320,672 Stein June 1, 1943 1,682,412 Palmer Aug. 28, 1928 164,897 Wood June 22, 1875 2,072,951 Johnson et al Mar. 9, 1937 1,472,827 Erdman Nov. 6, 1923 2,385,330 Candee et al Sept. 25, 1945 

